Mobile communications systems, such as cellular or personal communications services (PCS) systems, are formed of a plurality of cells. Each cell provides a radio communications center in which a mobile station establishes a call with another mobile station or a wireline station connected to a public switched telephone network (PSTN). Each cell includes a radio base station, with each base station connected to a mobile switching center that controls processing of calls between or among mobile stations or mobile stations and PSTN stations.
Various mobile communications protocols have been developed and implemented. One such protocol is the time-division multiple access (TDMA) protocol, with one version being the IS-136 standard (TIA/EIA-136) from the Telecommunications Industry Association (TIA). With IS-136 TDMA, each channel carries a frame that is divided into six time slots. Another TDMA-based protocol is the Global System for Mobile (GSM) protocol from the European Telecommunications Standards Institute (ETSI), which uses a TDMA frame divided into eight time slots.
Control signaling and bearer traffic (e.g., voice, data) is communicated over radio frequency (RF) carrier signals transmitted in both uplink (from mobile station to base station) and downlink (from base station to mobile station) directions. The RF carrier signals used in a mobile communications network are defined within an allocated frequency band or spectrum. Several frequency bands are allocated by governmental entities for use by wireless service providers in mobile communications networks.
Typically, the number of available carriers within each frequency band is relatively limited. To effectively use the limited carrier frequency band in a target coverage area, a frequency reuse pattern is implemented. In a frequency reuse pattern, groups of carrier frequencies are reused at regular distance intervals. In a traditional frequency reuse pattern, a predetermined number of cells are grouped into a cluster. The available carrier frequencies are then assigned to each cluster, with the number of carrier frequencies of each cluster divided among the number of cells in the cluster.
In a conventional mobile communications system, a block of available carrier frequencies are reserved for certain types of control signaling. One such control signaling is beacon control signaling, such as the broadcast control channel (BCCH) in a GSM mobile communications network. The BCCH is continuously transmitted by a base station in each cell, typically at full power, to provide certain types of information for mobile stations to use when the mobile stations first power up in a cell or transition from neighboring cells.
The reserved block of carrier frequencies is unavailable for communicating bearer traffic (e.g., voice, data, etc.) in any of the cells. As a result, the available bandwidth for communicating bearer traffic is further limited.